1. Field of the Invention
This invention relates to packaging materials, particularly for packaging foodstuffs.
2. Description of Related Art
Packaging materials of the sheet-type are well known. Such materials include plastics films, polyolefins, foils (including aluminium foil) and papers. It is also known to print Trade Marks, labelling and other information onto such sheet-type materials and to apply an overprint varnish over the printing in order to protect it. However such overprint varnishes have generally been solvent-based, which can give rise to environmental problems. In addition, an adhesive is applied to selected areas of the rear face of the material, for the purpose of sealing a packaging article made with the sheet material. Such adhesive must not adhere to the front face of the material when it is being stored, for example in a roll, prior to use, but must act to seal the packaging article when two sheets of the material are brought together, rear face to rear face, under pressure. Although a cold seal adhesive is known for this purpose, it has been difficult to get this adhesive to adhere on certain sheet-type materials without a solvent-based primer.